1. Field of the Invention
This invention relates to inhibition of body odor, and more particularly to an optically active deodorant ingredient, deodorant composition containing said ingredient, and a method for inhibiting malodor formation by applying such composition.
2. Description of the Prior Art
As is well known, the mechanism of formation of the most common type of body odor is based upon the action of microorganisms on eccrine and apocrine sweat. Axillary bacteria act on the proteinaceous secretions present in sweat to produce the pungent odor known as axillary malodor. As a consequence of this mechanism there are in wide commercial use today in the over-the-counter toiletries and cosmetics category two types of products that inhibit body odor, deodorants and antiperspirants, the latter group also occasionally referred to as antiperspirant/deodorants. The former group is meant to include products containing an active material which inhibits the growth of microorganisms present on the skin and thereby prevent their action on sweat to produce odoriferous substances. The latter group is meant to include products which contain materials that inhibit sweating in the first place. For various reasons, such as aesthetic preference, sensitivity to certain astringent antiperspirant salts, etc., individual consumers who wish to use a product in this broad category may prefer one or the other type. The present invention is particularly concerned with improvements in deodorants.
Current deodorants are generally of two types: odor maskers and germicides. Despite the many disclosures in the art pertaining to deodorant compositions, current products are not sufficient to suppress odor in a significant proportion of the population, particularly during periods of "stress." Thus, there remains a need for deodorant compositions and methods which are effective, safe and economical.
It is well known that many deodorant products contain ingredients which inhibit the growth of axillary bacteria. However, not all "bacteristatic" or "bactericidal" compounds will necessarily produce good deodorant products for several reasons. First, although many strains and species of bacteria exist, only a very few specific strains colonize the surface of the skin in the axilla and are responsible for producing axillary malodor. Bacteristatic and bactericidal compounds exhibit a wide range of potencies against any particular given bacterial strain, for example, a particular compound may be highly potent against one strain but yet completely ineffective against another. Good antibacterial deodorant compounds must therefore be effective against the specific strains of axillary bacteria which cause malodor. Secondly, good antibacterial deodorant ingredients need to maintain their activity for the desired length of time in the axilla. This means they must be physically, chemically, arid biochemically compatible with the product formulation and the environmental conditions of the axilla, and they must be sufficiently adherent to the skin so they are not rinsed or rubbed off. Thirdly, the compound needs to be safe, that is, non-toxic to the body and non-irritating to the skin with daily application of amounts which effectively inhibit the growth of axillary bacteria. Again, not just any anti-bacterial compound will fulfill these requirements. Thus, discovering a good antibacterial deodorant ingredient that will be clinically safe and effective for controlling axial malodor is far from a trivial task. This can be attested to by the fact that among the many hundreds of known antibacterial compounds, there are relatively few that have been successfully used in deodorant products.
While known deodorants usually have good antimicrobial properties, it does not follow that good antimicrobials will be effective as deodorants. For example, the following antimicrobial materials were tested for deodorant activity, and no improvement over currently available materials was observed; in some cases no deodorant activity was observed at all: hydrogen peroxide, chlorhexidine, triacetin, and 3-(trimethoxysilyl)propyloctadecyldimethyl ammonium chloride (Dow-Corning, Q9-5700). Other workers have also noted this poor correlation between antimicrobial activity and deodorant activity; see, for example, Dravnieks, Krotoszynski, Lieb, and Jungermann, "Influence of an Antibacterial Soap on Various Effluents from Axillae," J.Soc. Cosmetic Chemists, 19, 611-626 (1968) and Cowen, "Relative Merits of `In Use` and Laboratory Methods for the Evaluation of Antimicrobial Products, "J. Soc. Cosmetic Chemists, 25, 307-323 (1974).
The ability of certain D-amino acids to inhibit bacterial cell wall synthesis is disclosed by Manning, et al., Proc. Nat. Acad. Sci. USA, 71: 417-421, (1974). These compounds have been used as systemic antibiotic products: however, such use was abandoned due to systemic side effects as disclosed by Patchett, A. A., et al., Soc. Chem. Ind. (Lond.) Monogr., 42: 109-118, 1989, presumably due to metabolism of the compounds by D-amino acid oxidase present in the kidney. Topical use of these compounds as antibacterial or deodorant products was not taught.
Alanine analogues, e.g., D-cycloserine and .beta.- chloro-D-alanine, among others, are known to exhibit antibiotic activity by inhibiting specific target enzymes, e.g., alanine racemase and D-alanine:D-alanine ligase, and D-amino acid transaminase. This interferes with the assembly of peptidoglycans, resulting in disruption of cell wall structure. See, Neuhaus, et al., Pharmac. Ther., Vol. 14, pp. 265 to 319. The reference also discloses in vitro synergistic antibacterial activity for a mixture of .beta.-fluoro-D-alanine and D-cycloserine (id. at 304).
The use of beta-halo-,alpha-halo-, or alpha-methyl-alanines, or cycloserine as inhibitors of bacterial malodor-producing enzymes (pyridoxal phosphate- or PLP-dependent enzymes) in deodorant products is disclosed in U.S. Pat. No. 5,487,886 to Lyon, et al. However, no mention is made therein of bactericidal activity such as bacterial cell wall synthesis or growth inhibition. Indeed, the reference teaches that cycloserine's deodorant activity results from its beta-lyase enzyme inhibition activity and further teaches away from the bactericide of the present invention by disclosing that trifluoroalanine and L-cycloserine had no inhibitory effect on the growth of Staphylococcus cells in culture. Moreover, the reference is silent with respect to D-isomers and does not disclose or suggest the use of D-amino acids inasmuch as it is directed to a mechanism for suppressing body odor by inhibiting amino acid .beta.-lyase enzyme using L-amino acids.
U.S. Pat. Nos. 5,213,791 and 5,595,728 disclose the testing of .beta.-substituted amino acids such as .beta.-chloroalanine as well as cycloserine for their activity against malodor-forming enzyme in the presence of whole cells.
Contrary to literature reports of studies using other bacterial strains, .beta.-halo-L-alanines are not effective for inhibiting bacterial cell wall synthesis and bacterial cell growth of malodor-producing strains of axillary bacteria. .beta.-halo-L-alanines also suffer from the disadvantage of inhibiting many other PLP-dependent enzymes in the skin and potentially other human tissues. For example, topical application of .beta.-chloro-L-alanine irreversibly inhibits serine-palmitoyl transferase in the skin, and alters recovery of skin barrier function in vivo as noted by Holleran, W. M., et al., J. Clinic. Invest. 88: 1338-1345, 1991. Thus, use of .beta.-halo-L-alanines suffers from a significant potential to cause skin irritation and other undesirable effects.
Accordingly, it would be desirable to provide a deodorant composition which exhibits effective deodorant activity without causing skin irritation or alteration of skin barrier function.